Brake drums for 92 C2500

[ahansel1229]

Looking at some other forums the 13 X 2.5 pads have a flat backing plate and the 13 X 3.5 have a concave shaped backing plate.

 

[pressureangle]

If you have your drums in hand, it's simple to measure them for width and diameter. You can measure close enough with the wheels on to be certain. In case your axle has been swapped;

GMC or Chevy 14-Bolt Rear Axle Identification Guide

Do you have a full-float or semi-float 14-bolt axle? Slide-on or stud mounted brake drum? This 14-bolt axle ID guide is for you.

lugnut4x4.com